Dionysius Exiguus
Hierarch
Commemorated September 1
Our father among the saints Dionysius Exiguus, also Dennis the Small, Dennis the Little or Dennis the Short - meaning humble, was a monastic theologian and canonist of the sixth century. An accomplished mathematician and astronomer, he is considered the inventor of the Christian calendar. His feast day is September 1.
Source: OrthodoxWiki
